In the common configuration of a high current capacity corrosive battery, positive and negative battery plates are submersed in an electrolytic solution. Within the battery, plates of the same polarity are interconnected by a battery strap, and the strap is usually connected to a battery post or terminal. The battery post passes through the battery case to the exterior and is exposed to make an electrical connection to the positive and negative plates of the battery by means of a battery cable clamp mounted on each terminal. The battery cable clamp is tightened around each battery post or terminal by means of a bolt and bolt hole in the clamp. Extending from and connected to the battery post hole of the battery clamp is an insulated battery cable which transports electrical current to a load, e.g., a motor starter. Such connections are now in common use in the automotive industry and elsewhere, and have been presented in U.S. Pat. No. 4,486,517, entitled "WET-CELL STORAGE BATTERY" to Bender; and U.S. Pat. No. 3,941,615, entitled "BATTERY CONSTRUCTION" to McDowall.
Batteries having corrosive electrolytes, such as nickel-, cadmium-, or lead-acid batteries, which employ conventional metal post and metal cable clamp pressure connections develop problems at several sites. First, there is corrosion of the interface surface between the post and the clamp; secondly, the seal between the post and the battery case may break and the electrolyte will migrate freely upon the metal battery posts and between the post and clamp interface surfaces thereby increasing the corrosion. When the electrolyte and the metal react chemically, moreover, a high electrical resistance is created and the electrical connection at the post-clamp interface is destroyed. Thirdly, the connection between the post and the plate strap inside the battery may break, stimulating the likelihood of sparking at the broken connection in the presence of hydrogen and oxygen gases, which results in explosions. Lastly, shorting of the electrically exposed posts and clamps can be quite dangerous.
When the conventional post-clamp interface, now in common use, becomes corroded, it must be cleaned and repaired in order to restore a reasonable electrical connection between the electrolyte and the terminal. In the process of cleaning the poast and the clamp, corroded material is removed until both surfaces are bright and clean, and the metal is uniformly exposed over the entire interface surfaces. After the corroded material has been removed, however, the post diameter is smaller, the inside diameter of the clamp is larger, and the optimum fit between the post and clamp has been destroyed. Repeated cleaning and maintenance of the connections eventually require that the battery cable clamp be replaced to restore a good electrical connection. But if the posts have been markedly reduced, an optimum fit may not be restored even with new cable clamps.
When a battery clamp is being removed for cleaning and reinstalled as described above, there is danger of over-torquing the clamp bolt and nut, especially if the bolt and nut are corroded and resist manipulation. Excessive torque on the battery clamp is transmitted to the battery post and the twisting of the battery post can break the post-to-case seal. When a post-to-case seal has been broken, the electrolyte will seep onto the post, the clamp, and the interfaces; requiring frequent maintenance and repair of the battery connections. As the frequency of cleaning and repairing the connections increases, more damage occurs at the post-case seal which in turn increases electrolyte migration resulting in still more degradation and greater unreliability of the system. Such operations continue until the battery is retired and replaced earlier than otherwise necessary.
Still another disadvantage demonstrated by the electrical connections currently in use is related to the connection between the posts and the battery plates within the battery case. The battery posts are connected internally to plate straps, one post each for the positive plates and for the negative plates. This battery post-plate strap connection can be broken when the battery clamp is over-torqued and those twisting forces are also transmitted to the post-plate strap connection. Once the post-to-case seal is broken as described earlier, the post-plate strap connection can be easily broken as well. At best, a broken internal connection can result in intermittent operation of the battery, but, at worse, an explosion can occur in the battery. If the internal post-plate strap connection is broken, a spark can occur at the broken interface, especially if the battery is being vibrated or mechanically shocked, as is likely to happen when the vehicle is in motion, or when the post is being manipulated manually. In a charged, charging, or especially in an overcharged battery, hydrogen and oxygen gas, produced by electrolysis of water, are present in the battery case. A spark in the presence of this atmosphere will cause an explosion which can break the case. In addition to the destructive explosion itself, the electrolyte, such as sulfuric acid, will splash over the surrounding surfaces and may cause burns or otherwise harm the worker.
The shorting of a preferred electrical path occurs when a less resistive pathway for the current is provided. An alternative electrical current pathway between the battery terminals is established by the migration of the battery electrolyte over the surface of the battery case when the posts are exposed. There are two main causes for electrolyte being on the surface of the battery. First, if the battery cells are overfilled with replenishment water, a dilute solution of the electrolyte spreads over the surface of the battery thereby constituting a current leakage path. Another cause, as previously mentioned, is a broken post-to-case seal. Cleaning the battery removes the current leakage path resulting from the first cause, but, in the second case, there is continuous migration of electrolyte on the battery surface. Such a current leakage path can cause a battery to be discharged, unless it is frequently recharged. Moreover, if a battery is near discharge while in use, and is being vibrated and shocked mechanically, plate material can be shaken off. This material falls to the bottom of the case, and, obviously, the capacity of the battery is reduced. Continuous separation of plate material will, of course, require that the battery be replaced before its expected term of life is reached. The presence of the electrolyte, such as sulfuric acid, on the surface of the battery, moreover, can cause skin and clothing burns. Elimination of surface leakage discharge also reduces or eliminates the nuisances and inconveniences of jump starting and recharging the battery.
Another possibility of shorting a common battery, such as a lead-acid automobile battery, arises because the battery has exposed terminals or posts. A tool, such as a wrench, can simultaneously contact both terminals easily, thereby providing an electrical pathway. Shorting of a high current battery can cause human injury by burns and explosions.
In order to prevent the aforementioned hazards and disadvantages associated with the maintenance and repair of the typical battery, special tools are required. Best practices call for a special clamp puller, a post brush, a clamp brush, and two wrenches used in removing a clamp from the post, cleaning the post, cleaning the clamp, and reinstalling the clamp on the post. If skill has not been developed in the operator and the special tools are not in hand, which is most often true, the possibility of damage to the battery and of an accident is considerably increased.
Attempts to prevent the above-mentioned shortcomings of the existing battery terminal connections have been presented in U.S. Pat. No. 4,331,749, entitled "STORAGE BATTERY STRUCTURE" to Beck; and U.S. Pat. No. 4,127,707, entitled "STORAGE BATTERY" to Ohya et al. Although the patent issued to Ohya teaches a storage battery with an improved seal between the terminal post and the battery cover, the invention, nonetheless, still presents external terminal posts for electrical connection from the battery itself to the battery load.
U.S. Pat. No. 4,331,749, entitled "STORAGE BATTERY STRUCTURE" to Beck presents a battery connection in which the battery conductors are connected directly to the interior plate straps. Note, however, that the electrical conductors are directly exposed to and immersed in the electrolyte. This arrangement presents the conductors as sacrificial elements to the battery electrolyte, thus providing for complete failure of electrical current transport means. The chemical reaction resulting from the exposure of the conductors to the electrolyte, moreover, produces hydrogen, an explosive gas, and copper sulfate, essentially a nonconductor, which will rapidly destroy the electrical conductor and contaminate the electrolyte and the battery plate materials.
The Beck invention presents other shortcomings overcome by the invention disclosed herein. The battery electrolyte and plate materials are easily contaminated. The plastic covering of the conductor provides a means of escape of the electrolyte from the battery and exposes the conductor to the electrolyte, resulting in complete destruction of the conductor within the plastic covering. Additionally, the terminal connections can be easily corroded because they are exposed to the transported electrolyte. Shorting is actually promoted and enhanced at the junction box presented in the Beck invention because the conducting surfaces are brought into closer proximity at the junction box than the posts of a standard battery. Lastly, there is a possibility of electrolyte leakage at the "grommet" interfaces with the conductor plastic covering and the battery case.